Circuit design CHALLENGE!

[mcbrood]

Hi guys,

I'm building a five string fretted with one EMG 40DC pickup, and I'm hoping someone can help me out with my wiring idea. I'm going for a super clean look, so I want to have only:

-a slider for volume
-one switch
-output jack

Slider: I can only get a 25k ohm slider in linear taper here in New Zealand, but am I correct that if I bridge a 5k ohm resistor across the pot then I will have an approximated audio taper?

Switch: My idea is to have a 3-way switch, middle position is a bypass straight to the jack from the volume control. That leaves me two other positions to play round with. My ideas are:

1. 'Tone switch': have a trim pot w/ capacitor inside the cavity. Trimpot can be set for desired treble roll-off so that the switch cuts the highs for reggae/vintage rock sounds.

2. 'Slap contour': Either an active or passive circuit that gives a modern slap sound.

Questions:
-Do you think this is a good idea?
-Anyone got any other ideas for the switch options?
-Can anyone help me design this circuit?


Very grateful for any opinions or help. Thanks

[line6man]

Stick with the linear taper. You will like it much better than the audio taper. Linear taper pots (well, in your case faders) have a much more even volume roll off.

How about a Series/Single Coil/Parallel switch?

I'll draw you a diagram when you make up your mind on what you want to do.

[R. Laevinus]

I can't tell you about bridging the fader, but can you not simply order an audio-log fader from the 'Net? Also, if I may ask, why are you using a fader and not a pot?

My 2 cents on this is that it's a bad idea. A fader will have a greater chance of getting knocked about, and that long slit has great potential to be both a lint-trap and an eyesore. Bear in mind that faders are open on the top - meaning that you're going to get gunk in there, making your signal all scratchy or even short it out completely. I vote go for a normal, sealed-shaft pot.


As for the tone switch, I've done this using a Gibson-style three-way selector on one of my basses. If you want I'll draw you a diagram of how I did it, but when the switch was left, it killed the signal - in the center, tone at 50% - right, tone bypass.

Hint - rather than a trimpot in the cavity, mount a normal, split-shaft pot in the cavity on a metal or plastic L-bracket, and line it up with a carefully drilled hole in the cavity cover - in this fashion you can adjust your tone any time with a guitar pick, but if everything is flush, you'll never 'accidentally' adjust it.

To be honest, even though I've done it, I don't reccommend it. You'll be pining after what you've lost - the freedom to adjust the tone - very quickly.

As per a slap tone... I'm not a slap player, so I don't know what makes a good slap tone. I'd reccomend that you use an outboard unit for it, though, as you will probably want much more than a one-trick pony for that - you'll probably want an adjustable 3-band EQ, at the very least. Theoretically you could use trimpots or recessed pots on the back, but then adjustments will be a pain. I vote get an EQ pedal or a DI with a good EQ - you can transfer that from bass to bass, too.



My suggestion? For a good, clean look, use a single stacked pot for vol/tone. Of if you really want that tone switch, use a push-pull pot for vol and tone.

Or if you really want that fader, do a fader and a tone knob.






...but if you really, really, really want a standalone tone switch, I can diagram that for you.

[line6man]

Originally Posted by R. Laevinus

My 2 cents on this is that it's a bad idea. A fader will have a greater chance of getting knocked about, and that long slit has great potential to be both a lint-trap and an eyesore. Bear in mind that faders are open on the top - meaning that you're going to get gunk in there, making your signal all scratchy or even short it out completely. I vote go for a normal, sealed-shaft pot.
.

+1

Originally Posted by R. Laevinus

As for the tone switch, I've done this using a Gibson-style three-way selector on one of my basses. If you want I'll draw you a diagram of how I did it, but when the switch was left, it killed the signal - in the center, tone at 50% - right, tone bypass.

What you did was connect the ground to the common terminal, the signal on one leg, and on the other leg a capacitor in series with a fixed resistor which connected to the signal, correct?

That's an interesting approach.

[mcbrood]

Stick with the linear taper. You will like it much better than the audio taper. Linear taper pots (well, in your case faders) have a much more even volume roll off.

How about a Series/Single Coil/Parallel switch?

My understanding was that volume pots are normally audio taper, whereas tone pots were often linear?? Don't think Series/Single/parallel is at all possible with a single EMG.

I can't tell you about bridging the fader, but can you not simply order an audio-log fader from the 'Net? Also, if I may ask, why are you using a fader and not a pot?

My 2 cents on this is that it's a bad idea. A fader will have a greater chance of getting knocked about, and that long slit has great potential to be both a lint-trap and an eyesore. Bear in mind that faders are open on the top - meaning that you're going to get gunk in there, making your signal all scratchy or even short it out completely. I vote go for a normal, sealed-shaft pot.

EMG needs 25K and I can't find a 25K audio taper fader anywhere (on this side of the world). Eyesore...I disagree, the reason I want it is for a different look to standard. Faders are used all the time in mixers, I don't see why a bass should be so different? I'm sure I could fashion a rubber slip over the fader to stop ingress.

Hint - rather than a trimpot in the cavity, mount a normal, split-shaft pot in the cavity on a metal or plastic L-bracket, and line it up with a carefully drilled hole in the cavity cover - in this fashion you can adjust your tone any time with a guitar pick, but if everything is flush, you'll never 'accidentally' adjust it.

Awesome idea - thanks.

To be honest, even though I've done it, I don't reccommend it. You'll be pining after what you've lost - the freedom to adjust the tone - very quickly.

Thing is - I want to do it. Check out the Anthony Jackson Fodera presentation - one pickup straight to the jack and it's no cheap bass. Just want something a bit different I guess.

Appreciate everyones input -thanks.

[mcbrood]

As per a slap tone... I'm not a slap player, so I don't know what makes a good slap tone. I'd reccomend that you use an outboard unit for it, though, as you will probably want much more than a one-trick pony for that - you'll probably want an adjustable 3-band EQ, at the very least. Theoretically you could use trimpots or recessed pots on the back, but then adjustments will be a pain. I vote get an EQ pedal or a DI with a good EQ - you can transfer that from bass to bass, too.

The idea for the slap switch came from an amp I used to have...a trace elliot with the smx12 pre-amp. The amp had two "pre-shapes" on the EQ. It's actually often really handy/cool to flick a switch and completely change your EQ. Rather than fiddling with a 3-band EQ or whatever to get what you want, every time you want to switch.

I thought it'd be cool to build some pre-sets like that into a bass.

Cheers!

[line6man]

Originally Posted by mcbrood

My understanding was that volume pots are normally audio taper, whereas tone pots were often linear?? Don't think Series/Single/parallel is at all possible with a single EMG.

Do a search on linear taper pots...
I've recently changed my stance on the matter. Linear taper pots really are the answer, even though it would seem that audio taper pots would work better.

Ah. I just did a search on the 40DC, and it appears to only have a two conductor output, so series/parallel and single coil options cannot be done.
FWIW, it has absolutely nothing to do with it being a single pickup. I'm talking about the individual coils inside the pickup.

[M0ses]

Originally Posted by R. Laevinus

Also, if I may ask, why are you using a fader and not a pot?

Because it would be effing cool. Not that your post wasn't immensely more valuable than my own. Personally I wouldn't go this option, either, really, because stacked volume/tone single knob basses are the shiztnit, too, and much easier to achieve.

[mcbrood]

Yep, it's pretty much style over function with the fader, and while that may seem silly I still wanna try it. Shuld be able to convert it back to rotary pots if needed as it's a zebrano top and I plan on putting the fader slit in one of the dark stripes... And the tone switch is just to build a little versatility into what is a very simple setup.

I believe none of the EMG active pickups are splittable etc. To accomplish that function on the guitar they have the '89 model, which has both a single coil and humbucker in a humbucker sized housing.

[Darkstrike]

Originally Posted by mcbrood

I believe none of the EMG active pickups are splittable etc. To accomplish that function on the guitar they have the '89 model, which has both a single coil and humbucker in a humbucker sized housing.

They have a bass humbucker with the same setup as the '89.

[M0ses]

Originally Posted by mcbrood

Yep, it's pretty much style over function with the fader, and while that may seem silly I still wanna try it.

DOOOO IIIIT and show me pictures please.

[mcbrood]

Could be a while before the bass is finished, but I will definately be posting pics and soundclips.

[Rickett Customs]

Originally Posted by Darkstrike

They have a bass humbucker with the same setup as the '89.

Yes, Any "active" with the suffix "TW", are regardless of guitar or bass models......89 being the exception.

[R. Laevinus]

Originally Posted by line6man

What you did was connect the ground to the common terminal, the signal on one leg, and on the other leg a capacitor in series with a fixed resistor which connected to the signal, correct?

Something like that. I did it a while back.


If the fader is a stylistic thing, knock yourself out! Just as long as you're aware there are drawbacks. As per the rubber dust-cover and mixers - if you look closely, you'll see this is exactly what better mixers do. Even so, the rubber usually gets bent into an open shape after a couple weeks of use, resulting in a need to keep the fader section squeaky clean or risk noise on the fader. As a 22-year-old male living alone, this is something of an issue for me. I'd imagine it would be worse on a bass, what with sweat and grime accumulating and fuzz from gig bag and hardcase linings... but hey, as long as you're making an informed decision.

As far as a style selector switch - sure, you can use a preset EQ that gets toggled on or off (or more accurately, in and out of the circuit) if you choose to do so - but take my advice and mount the pots under holes on the cavity cover, so that they can be adjusted with a screwdriver or a guitar pick without having to remove the cover. It'll still be a pain to adjust them, but far less of a pain than if you had to take the cover off.

And DON'T just decide a cavity cover isn't necessary - you'll be opening yourself up to electronic noise, short-circuits, and components getting knocked around.

I wanna see how this turns out!

P.S. - if you're going to have active electronics in there anyway, have you thought about an illuminated fader, for a really boutique look?

[MooseLumps]

Originally Posted by R. Laevinus

As per a slap tone... I'm not a slap player, so I don't know what makes a good slap tone. I'd reccomend that you use an outboard unit for it, though, as you will probably want much more than a one-trick pony for that - you'll probably want an adjustable 3-band EQ, at the very least. Theoretically you could use trimpots or recessed pots on the back, but then adjustments will be a pain. I vote get an EQ pedal or a DI with a good EQ - you can transfer that from bass to bass, too.

I've used basses where the slap contour is fixed unless you open the control cavity to turn the mini trim pots, and let me tell you, it's handy to have the switch


until anything whatsoever changes in your configuration. going to perform in a different room is a good example. Suddenly your sweet slap tone is like an aluminum foil and wood screw pipebomb going off behind you, and you can't adjust it at all because you are in the middle of a gig.

...your call.

[mcbrood]

And DON'T just decide a cavity cover isn't necessary - you'll be opening yourself up to electronic noise, short-circuits, and components getting knocked around.

I wanna see how this turns out!

P.S. - if you're going to have active electronics in there anyway, have you thought about an illuminated fader, for a really boutique look?

I plan on having the cavity cover secured by magnets, so that access to any trimpots etc is simple.

I thought about mounting an amber LED under the fader, but the necessity of letting light out will allow dust etc in...unless you have any ideas around that?

I've used basses where the slap contour is fixed unless you open the control cavity to turn the mini trim pots, and let me tell you, it's handy to have the switch


until anything whatsoever changes in your configuration. going to perform in a different room is a good example. Suddenly your sweet slap tone is like an aluminum foil and wood screw pipebomb going off behind you, and you can't adjust it at all because you are in the middle of a gig.

...your call.

I'm building the bass for me, not to sell, and as I don't have a variety of amps etc I figure I can risk it... the logic is that knobs can always be added later on, but it's much more difficult to take them back once installed...a bit of adjustment at the amp and/or by a soundman pre-gig should account for differences in a room.

Thanks everyone!

[mcbrood]

Keep the ideas coming...! I'm particularly interested if anyone has a circuit for a slap contour that they'd be willing to share.

I'm leaning towards mounting a standard tone knob/slap contour controls inside the cavity so that tinkering is easy. But may go with trimpots to keep it compact...not sure.

Cheers.

[mcbrood]

If anyone is interested...here is the article where I got the idea about bridging a linear pot with a resistor to make a log (audio) taper. Apperently it actually makes a better log taper than commercial log pots (which are essentially two linear sections of different resistance slope joined together to approximate the log taper).

Enjoy:

http://www.geofex.com/article_folder...s/potscret.htm

[R. Laevinus]

Originally Posted by mcbrood

I plan on having the cavity cover secured by magnets, so that access to any trimpots etc is simple.

I thought about mounting an amber LED under the fader, but the necessity of letting light out will allow dust etc in...unless you have any ideas around that?

I don't think magnets is a good idea. I could be wrong, but I would suspect that magnets strong enough to hold a cover in place securely would also be strong enough to set up a field that could, through the vibrations inherent in a bass being played, mess with your signals, particularly if you've got active components happening. I also suspect that such creatures would be kind of a pain in general. I vote you go with a traditional screwed-on cover, with holes drilled for trimpot access. If you want to get really fancy, you could go for a hinged and latched cover, or even a slide-out wood panel, however I stand by my reccomendation for holes for pot access.

As per the light-up fader - I know that faders are available with an LED in the handle pit, a la MXR EQ boxes. Check on Mouser to start with - I know they exist, although I'm not 100% where to get one or if they'll do what you need. It's an idea worth looking into, though.

As per the slap contour - just get yourself a standard three-band EQ, and set the cavity-mounted pots to how you like it. Then set the switch to toggle the EQ in and out of the circuit. If you can't find an EQ sans pre, you can also rig a second volume trimpot in line with the switch to even out the passive/EQ'd volume.

[R. Laevinus]

HEY - AN IDEA!!!

Try this on for size:

If I understand correctly, you don't want a pile of knobs on the front of the axe cluttering up your looks, right? Cool, I dig it.

However, the options are currently none too good - trimpots (pain to adjust) or fixed-value circuits (PITA in general).

So dig this: Why don't you route a recess into the back of the axe, and mount pots - complete with full-size metal dome knobs - there, for all the features you want, but not on the front of your axe?

If you do it right, your controls will be recessed beneath the surface of the body, meaning it would be difficult to accidentally adjust them. Even if some article of clothing did swipe them, the smooth, rounded knob tops would result in minimal - if any - change in settings. But it would be a swanky look, even from the back - MUCH better than trimpots - and the freedom you'd have in potential adjustments would be very nearly as good as with front-mounted pots!

Whaddaya think?